AJP - Regulatory, Integrative and Comparative Physiology, Vol 268, Issue 3 666-R675, Copyright © 1995 by American Physiological Society
Responses of single neurons in amygdala to interoceptive and exteroceptive stimuli in conscious cats
M. M. Knuepfer, A. Eismann, I. Schutze, H. Stumpf and G. Stock
I. Physiologisches Institut, Universitat Heidelberg, Germany.
The amygdala is critical for behavioral arousal and must therefore
integrate a wide variety of inputs. We examined sensory inputs and the
degree of convergence to single neurons in the amygdala in conscious freely
moving cats. A pressor stimulus elicited responses, predominantly
inhibitory, in one-half of the amygdalar neurons tested. Most neurons in
the central and basal nuclei responded to carotid chemoreceptor activation
typically with an excitation. Almost one-half of all amygdalar neurons
tested, particularly in the central nucleus, received orthodromic input
from the locus ceruleus, the substantia nigra, and/or the contralateral
central nucleus of the amygdala. Exteroceptive sensory stimulation with
optic, acoustic, tactile, and olfactory stimuli elicited responses in 33,
55, 39, and 59% of amygdalar neurons, respectively. Two-thirds of the
neurons tested with more than one external stimulus modality responded in
the same manner to the various stimuli (usually excitation), demonstrating
a convergence of exteroceptive stimuli on single amygdalar neurons,
particularly in the basal nucleus. Spontaneous and induced behavioral
arousal elicited responses in 92 and 86% of neurons, respectively. Most
neurons responded to multimodal exteroceptive stimuli and behavioral
arousal in the same manner. We suggest that amygdalar inputs are highly
varied and, in many cases, relatively nonspecific and that the amygdala
integrates a large number of external and internal sensory modalities to
regulate autonomic and behavioral responsiveness to various stimuli.
